The field of this invention relates to a method of anchoring, sealing and circulating between a casing string and inner string therein.
With the use of casing strings in wells, having small clearances between each string, it has become more common to run the casing string open ended to allow the fluid below the casing to escape through the inside of the casing to prevent an increase in pressure in the well that could break down the formation and cause a well control problem.
In order to run a casing string of this type into a sub sea well head it is necessary to run the casing inside the riser then attach a casing hanger and running tool to the casing and run the assembly in the well to the sub, sea tree using drill pipe. Normally the casing can then be cemented in place using conventional cementing plugs located at the hanger running tool and launched by dropping a ball or other device from the rig floor. In some instances it is desirable to run pipe below the hanger running tool to or near the bottom of the casing being run. This will eliminate the need for cementing plugs since there is no need to wipe the casing with cementing wiper plugs.
Should the well begin to flow the blow out preventer can be closed on the casing string isolating the annulus between the casing string being run and the well bore. The drill pipe being run inside the casing can also be isolated by connecting it to a top drive or by attaching a safety valve to the upper most joint of drill pipe. However this leaves the casing drill pipe (inner string) annulus open thereby exposing the well to extreme danger.
It is therefore clear there is a need for a device to isolate the annulus between the inner string and the casing string during the process of running the inner string inside the casing string.
Not only is it desirable to isolate this annulus space by placing a seal between the two members, it is also necessary to anchor the inner string to the casing string to prevent internal pressure in the casing string from pushing the inner string out of the well.
It is therefore clear there is a need for a device to anchor the inner string to the casing to prevent it from dropping into the well or being blown out of the well.
Should a gas bubble exist it must be circulated out of the well to place the well back under control. In order to circulate the well it is common practice to pump mud into the most inner string, in this case the drill pipe or inner string and out the annulus around the drill pipe.
It is therefore clear there is a need for a device to provide a means of circulating fluid through the well.
A device is disclosed that can be attached to the upper end of the casing string or casing hanger that will anchor the inner string to the casing to prevent it from moving. A seal is also disclosed that will seal the annulus between the inner string and casing at the surface, the device also provides for circulating fluid through the annulus space between the casing string and inner string.
Accordingly, it is an object of the present invention to provide a apparatus useful for anchoring, sealing and providing a circulation path in a casing string having an inner string. Accordingly, an apparatus is disclosed that provides for attaching and sealing to the upper end of the casing string or hanger and provides for the inner string to be run through the apparatus. A means of anchoring the inner string to the apparatus is also provided. Accordingly, an apparatus that provides a flow path for circulating fluid is disclosed. These and other objectives accomplished by the apparatus will become more apparent from a review of the detailed description below.
A apparatus is disclosed for attaching and sealing to the upper end of the casing allowing the inner string to be run through the apparatus. The apparatus provides a latch for anchoring the inner string and a seal for sealing on the inner string. Also disclosed is a flow path for providing for circulation of fluid between the inner string and casing annulus. Also disclosed is an inner string sub that provides a profile anchoring and sealing the inner string by the apparatus.
For running the inner string the apparatus provides an opening that does not restrict the passage of the tool joints of the inner string. Once it is decided to anchor or seal on the inner string the inner string sub is attached to the upper most joint of the inner string. This inner string sub is then lowered into the apparatus until the latching profile and seal area of the inner string sub is adjacent the latch and seal in the apparatus. The latch is then set by hydraulic pressure. The latch is tested by pulling or pushing (raising or lowering) the inner string. The seal can then be set by hydraulic pressure. Circulating fluid either into the casing inner string annulus or the inner string can test the seal.